Have you ever been arrested? Imagine the question not appearing in the solitude of your thoughts as you read this paper, but appearing explicitly whenever someone queries your name in a search engine. […] Appearing alongside your list of accomplishments is an advertisement implying you may have a criminal record, whether you actually have one or not. Worse, the ads don’t appear for your competitors. Source

Sweeney gathered this evidence by collecting over 2000 names that were suggestive of race. For example, first names such as Trevon, Lakisha and Darnell suggest the owner is black while names like Laurie, Brendan and Katie suggest the owner is white.

She then entered these plus surnames into Google.com and Reuters.com and examined the ads they returned. Most names generated ads for public records. However, black-identifying names turned out to be much more likely than white-identifying names to generate ads that including the word “arrest” (60 per cent versus 48 per cent). Source

Though “there is less than a 0.1% probability” that these findings “can be explained by chance” the report does not explain why this discrimination occurs, partly because this is outside the scope of the research but also because more information about the workings of Google AdSense is required.